I was at the range the other day and it was about 75-80 degrees. A guy there said we shouldn't be leaving our guns in the cases in the sun because it can warp/burnout our barrels. Now I've heard of waiting between groups when its hot but not this.

Also he was saying he met a guy who loaded shotgun shells with poweder that wasn't suppose to be used in hot weather and he blew up his gun in 90 degree weather. Is this possible or do you think this guy had of made a super hot load with a lot of shot.